modules: support running more than one simple app

Now since we have support for parallel launching in the command line
we can implement support for it in the modules.

Example (image config):

 run = [
   api.require('netperf').default,
   api.require('mgmt').shell
 ]

Result:

$ scripts/run.py
OSv v0.05-132-g779307c
Starting netserver with host 'IN(6)ADDR_ANY' port '12865' and family AF_INET

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Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>